For years, since the arrival of the drop-ceiling, Troffer drop-in fixtures have been used to light areas covered by such ceilings along with can lights and a few standard light fixture conversions. As the recessed drop-in Troffers go, (the 1′×4′, the 2′×4′ and the 2′×2′), they have all been nearly the same in regard to aesthetics. All have been designed with the light emitters or bulbs within the fixture located above the ceiling plane with a cover lens the same size as the light opening or have a simple grid within the opening, neither having much architectural design or artistic value. There are several issues with these fixtures, whether they are T8 or T5 fluorescents or even LED retrofit kits or LED replacement fixtures. Since the light source is above the ceiling plane, it does not spread the light evenly from wall bottom to wall top. In addition, recessed drop-in Troffers do not address the issue of heat build-up within the fixture.
In the realm of thermal management of small electric components, such as computer modules, chips, PC components and LED heat dissipation needs, there exists a variety of convection type and fan controlled heat sinks. Within this same arena, there is also a rising array of liquid cooled thermal management systems designed to remove unwanted, detrimental heat. There are basically three main types of cooling systems with variations of each. First and most prevalent are the simple convection heat sinks made primarily of aluminum or copper which allow heat to transfer from the component into the heat sink and then convect into the surrounding air. Second, and more effective, is combining the heat sink with a fan to accelerate the convection process. Third, and very effective though usually much bulkier, is the liquid cooled thermal transfer method consisting of a heat sink with embedded tubing containing a coolant or a radiator and a fan to cool the fluid or vapor. All three systems have their pros and cons.
A simple heat sink has the following pros: inexpensive and easy to manipulate size and shape to fit an area; no electrical devices such as fans that add cost and pose possible failure issues; and silent in operation. A simple heat sink has the following cons: convection is slow in comparison with moving air systems; and convection is very limited in the ability to efficiently remove heat, thus, is only useable in small or mild heat applications.
A combined fan and heat sink has the following pros: moving air is far more effective in forcing convection, speeding up heat thermal elimination; and fans are not very expensive and have a fairly long lifespan. A combined fan and heat sink has the following cons: fans increase the size and add to labor and time as they are an electric component; failure of the fan can cause overheating and damage to the component it is used to cool; fans produce noise; and fans consume energy.
Liquid cooling systems have the following pros: very effective in removing heat; able to cool larger more difficult components; and price is becoming more affordable. Liquid cooling systems have the following cons: currently, still relatively expensive; most efficient liquid coolers are much larger than alternate systems limiting their usage; due to the necessity of the fan to cool the liquid or vapor, failure is a possibility which will cause serious damage to the component it is to cool; the fan aspect produces noise; and the fan aspect consumes energy.
The use of Peltier Plates is another method of cooling components. The Peltier Plates method is, however, expensive and uses a fair amount of energy just to generate a cooling effect on one side while, at the same time, it builds heat on the other side that can cause a very hot surrounding especially if an additional fan is not used. This actually creates two possible points of failure: failure of the Peltier Plate itself or failure of the cooling fan, wherein either failure would, in most applications, cause damage to the component it is used to cool.
What is needed is a thermal system that has the advantages of the cheaper convection heat sink and yet has the effectiveness of a fan or liquid cooling system by accelerating the convection cycle while eliminating the cons associated with the fan-based cooling systems. It is an object of the present invention to provide a cooling system that moves air without the addition of extra electrical devices.
In accordance with one form of this invention, there is provided a lighting fixture adapted to be installed on a ceiling having a predetermined plane. A light emitting diode source is supported by the lighting fixture. At least a portion of the lighting fixture protrudes below the plane of the ceiling.
In accordance with another form of this invention, there is provided a lighting fixture which includes a light emitting diode light source. The light emitting diode light source has a front side which emits light and a back side opposite the front side. A primary heat sink is attached to the back side of the light emitting diode light source. Preferably, a divider plate is used to create two separate planes. A thermally conductive material is recommended for the divider plate, such as aluminum, copper or other such material allowing greater thermal surface for heat transfer. A pass-through or cross-over vent or vents are preferably used to allow air to pass from the lower plane to the upper plane via said heat sink, mounted below the divider plate. Preferably, a void is incorporated in the heat sink's center and this void is situated directly in line and under one of the divider plate vent openings, allowing heated air to pass from the lower plane to the upper plane. To be more efficient, a secondary heat sink is preferably mounted directly above the primary heat sink via the divider plate and directly above the vent pass-through. The primary heat sink center void may remain hollow or created with thermal posts, rings or a cone, depending upon the LED or LED array used to develop the most effective thermal transfer method for the desired LED/LED array. This dual plane development for heat transfer creates a thermal chimney or “air thermal pump” which, due to the physics of moving heat or heated air upward through the cross-over vent, creates a partial vacuum in the lower plane and primary heat sink which, in turn, draws cool air into said lower plane. This system thus accelerates the thermal exchange and increases the cooling capabilities of the heat sink.